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Description

Asian lady beetles are between 4.8 and 7.5 mm long. Their elytra, covering a pair of membranous wings, occur in different shades ranging from yellow, orange and red to black and have anywhere from 0 to 20 spots. In Canada, the most common form is orange with 19 black spots.

The pronotum, which covers the front of the thorax just behind the head, has two football-shaped pale eye spots.

Life cycle

Adults leave their shelter in the spring to mate. The eggs are laid on the underside of leaves, often near an aphid colony, for the larvae to feed on. Females produce hundreds of eggs, which hatch three to five days later. Larvae resemble tiny alligators, first light grey then black with yellow, orange or red spots and are covered with spines and tubercles. Larvae moult three times in two weeks. The mature larvae attach themselves to the undersides of leaves and transform into the pupal stage. The last moult takes place one week later, when the adult beetle emerges. Asian lady beetles congregate in October and look for a place to spend the winter.

They produce probably two generations a year in Quebec, maybe three if the summer is long and hot.

Geographic distribution

The Asian lady beetle is native to Japan, China and Korea, among other countries.

It was first successfully introduced to North America in 1988, in Louisiana. Since then, the beetle has spread across the United States and moved into Quebec, establishing itself in the southern part of the province as far as the upper Laurentians.

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Habitat

It is a primarily arboreal species that lives in gardens and fields and on farms and can be found on both hardwood and softwood trees.

Ill-suited to our northern climate, they must spend winter indoors to survive. This is why they are often found in our homes.

Diet

This is a predatory species that feeds on a wide variety of small insects. Aphids are a favourite food and adults can eat quite a few on a daily basis. Larvae feed on aphids, nectar and pollen.

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Interesting facts

Even beneficial insects can become pests when too many of them find their way into our homes. To avoid this problem, seal openings and gaps, especially around doors and windows, as well as the foundation and siding to prevent them from entering. Cover air vents, repair screens, and avoid leaving doors and windows open in the fall. If lady beetles have moved in, use a vacuum cleaner to suck them up, making sure to empty the bag right away.

Ecological roles

This lady beetle is an important predator of aphids and small insects that attack plants and is used as a form of biological pest control by cash crop growers and agriculturalists. Asian lady beetles are a food source for many animals.